An orthogonal frequency division multiplexing (OFDM) system is a transmission system that can effectively reduce selective frequency fading due to a delay spread by dividing one high-speed data stream into multiple low-speed data streams and transmitting the multiple low-speed data streams at the same time by using inter-orthogonal subcarriers.
An orthogonal frequency division multiple access (OFDMA) system, which is one of multiple access systems based on the OFDM system, can independently allocate one or more subcarriers to each user at a user request. Subchannels set as a group of the subcarriers are basic frequency resource units allocated to users. Since the subchannels are physically independent from each other, multiple access interference is not generated in the same cell.
However, in an OFDMA multiple cell system, interference which base stations that manage cells adjacent to one cell (hereinafter referred to as “central cell”) give to a user who uses the central cell, i.e., inter-cell interference (ICI), occurs. In order to reduce the inter-cell interference, not only a channel of the central cell but also channels of signals transmitted from the adjacent cells need to be estimated. That is, the OFDMA system needs to estimate the channel by considering interference caused by the adjacent cells.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.